<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>后盾人</title>
    <style>
        div {
            width: 200px;
            height: 200px;
        }

        div:nth-of-type(1) {
            border: solid 3px red;
            /* float: left; */
        }

        div:nth-of-type(2) {
            background: blue;
            float: left;
        }
    </style>
</head>

<body>
    <div></div>
    <div></div>
</body>

</html>